using System;
using System.Text;

/// <summary>
/// Performs AES (Advanced Encryption Standard) cryptography
/// see: http://msdn.microsoft.com/msdnmag/issues/03/11/AES/
/// </summary>
namespace MerlinEncrypt
{
	internal class clsAES
	{
		public enum KeySize { Bits128, Bits192, Bits256 };  // key size, in bits, for construtor

		private int Nb;         // block size in 32-bit words.  Always 4 for AES.  (128 bits).
		private int Nk;         // key size in 32-bit words.  4, 6, 8.  (128, 192, 256 bits).
		private int Nr;         // number of rounds. 10, 12, 14.

		private byte[] key;     // the seed key. size will be 4 * keySize from ctor.
		private byte[,] Sbox;   // Substitution box
		private byte[,] iSbox;  // inverse Substitution box 
		private byte[,] w;      // key schedule array. 
		private byte[,] Rcon;   // Round constants.
		private byte[,] State;  // State matrix

		private const int BlockSize = 16; // block size for encrypt and decrypt. should always be 16

		// events
		internal delegate void AES_EncryptDecryptEventHandler(int PercentageEncrypted, bool Encrypting);
		internal static event AES_EncryptDecryptEventHandler AES_EncryptDecryptEvent;

		#region Initialize

		/// <summary>
		/// Initializes the AES engine
		/// </summary>
		/// <param name="keySize">Size of the key</param>
		/// <param name="Password">the password</param>
		public clsAES(KeySize keySize, string Password)
		{
			// convert the password to a byte array, then call the other init func
			byte[] keyBytes = ConvertStringToByteArray(Password);
			Init(keySize, keyBytes);
		}

		/// <summary>
		/// Initializes the AES engine
		/// </summary>
		/// <param name="keySize">Size of the key</param>
		/// <param name="keyBytes">the password, in a byte array</param>
		public clsAES(KeySize keySize, byte[] keyBytes)
		{
			Init(keySize, keyBytes);
		}  // Aes constructor

		private void Init(KeySize keySize, byte[] keyBytes)
		{
			int i = 0;
			int keyLen = 0, kbLen = 0;
			byte nextByte = 1;

			try
			{
				SetNbNkNr(keySize);

				// set the key
				this.key = new byte[this.Nk * 4];  // 16, 24, 32 bytes

				// if the password is the right size, just copy the array
				if (this.key.Length == keyBytes.Length)
					keyBytes.CopyTo(this.key, 0);
				else // password is different size, so manually copy
				{
					// get the key lengths
					keyLen = this.key.Length;
					kbLen = keyBytes.Length;

					// manuually add the password
					for (i = 0; i < keyLen; i++)
					{
						// make sure we can use the keyBytes
						if (i < kbLen)
							this.key[i] = keyBytes[i];
						else // we need to add some extra bytes
							this.key[i] = nextByte++;
					}
				}

				// build the two matrixes
				BuildSbox();
				BuildInvSbox();
				BuildRcon();
				KeyExpansion();  // expand the seed key into a key schedule and store in w
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Init"); }
		}

		#endregion // Initialize

		#region Public Encrypt and Decrypt

		/// <summary>
		/// Encrypts the input string
		/// </summary>
		/// <param name="input">the string to encrypt  -   
		/// Note: the base encryptiong algorithm uses a byte array, but it's not always
		/// possible to convert the byte array to a string, using a 1:1 conversion.
		/// Instead, we will convert each byte to a string, and add a space. So,
		/// when you are encrypting a string, the return result will always be larger
		/// in length than the original. When you are decrypting a string, the return
		/// result will always be smaller in length than the original encrypted string.
		/// </param>
		public string Encrypt(string input)
		{
			string rText = string.Empty;

			try
			{
				// convert the string to a byte
				byte[] bInput = ConvertStringToByteArray(System.Text.RegularExpressions.Regex.Replace(input, "\r\n", "<crn>"));

				// encrypt
				byte[] bText = Encrypt(bInput);

				// convert the byte array to a string
				rText = ConvertByteArrayToEncryptedByteString(bText);
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Encrypt"); }

			// return the text
			return rText;
		}

		/// <summary>
		/// Encrypts the input byte array
		/// </summary>
		/// <param name="input">the byte array to encrypt</param>
		public byte[] Encrypt(byte[] input)
		{
			int i = 0, iLen = input.Length;
			byte[] output = new byte[0];
			byte[] newInput;
			byte[] inBuffer = new byte[BlockSize];
			byte[] buffer = new byte[BlockSize];
			int count = 0;

			try
			{
				// we need to resize the arrays so they are 16 byte blocks
				count = GetArraySize(input.Length);
				output = new byte[count];
				newInput = new byte[count];

				// copy the data from input to newInput
				System.Array.Copy(input, 0, newInput, 0, input.Length);

				// we need to send the cipher function 16 bytes at a time to encrypt
				for (i = 0; i < iLen; i = i + BlockSize)
				{
					// copy the input into the input buffer array
					System.Array.Copy(newInput, i, inBuffer, 0, BlockSize); // copy all 16 bytes

					// encrypt this block
					System.Array.Copy(Cipher(inBuffer), 0, output, i, BlockSize);

					// raise the event if necessary
					if (AES_EncryptDecryptEvent != null)
						AES_EncryptDecryptEvent(System.Convert.ToInt32(((double)i / (double)iLen) * 100), true);
				}
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Encrypt"); }

			// return the byte array
			return output;
		}

		/// <summary>
		/// Decrypts the input string
		/// </summary>
		/// <param name="input">the string to decrypt  -  
		/// Note: the base encryption algorithm uses a byte array, but it's not always
		/// possible to convert the byte array to a string, using a 1:1 conversion.
		/// Instead, we converted each byte to a string, and added a space. So,
		/// when you are encrypting a string, the return result will always be larger
		/// in length than the original. When you are decrypting a string, the return
		/// result will always be smaller in length than the original encrypted string.
		/// </param>
		public string Decrypt(string input)
		{
			string rText = string.Empty;

			try
			{
				// convert the string to a byte array
				byte[] bInput = ConvertEncryptedByteStringToByteArray(input);

				// decrypt and convert to the byte array to a string
				rText = System.Text.RegularExpressions.Regex.Replace(ConvertByteArrayToString(Decrypt(bInput)), "<crn>", "\r\n"); ;
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Decrypt"); }

			// return
			return rText;
		}

		/// <summary>
		/// Decrypts the input byte array
		/// </summary>
		/// <param name="input">the byte array to decrypt</param>
		public byte[] Decrypt(byte[] input)
		{
			int i = 0, iLen = input.Length;
			byte[] inBuffer = new byte[BlockSize];
			byte[] buffer = new byte[BlockSize];
			byte[] output = new byte[input.Length];

			try
			{
				// we need to send the cipher function 16 bytes at a time to encrypt
				for (i = 0; i < iLen; i = i + BlockSize)
				{
					// copy the input into the input buffer array
					System.Array.Copy(input, i, inBuffer, 0, BlockSize); // copy all 16 bytes

					// decrypt this block
					System.Array.Copy(InvCipher(inBuffer), 0, output, i, BlockSize);

					// raise the event if necessary
					if (AES_EncryptDecryptEvent != null)
						AES_EncryptDecryptEvent(System.Convert.ToInt32(((double)i / (double)iLen) * 100), false);
				}
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Decrypt"); }

			// return the byte array
			return output;
		}

		#endregion // Public Encrypt and Decrypt

		#region Private Encrypt and Decrypt

		/// <summary>
		/// Encrypt the data in a 16 bit block. returns:
		/// 16 byte block of encrypted characters
		/// </summary>
		/// <param name="input">16 byte block of characters to encrypt</param>
		/// <param name="retCount">the number of bytes actually used</param>
		/// <returns>16 byte block of encrypted characters</returns>
		private byte[] Cipher(byte[] input)  // encipher 16-bit input
		{
			byte[] output = new byte[16];

			try
			{
				// state = input
				this.State = new byte[4, Nb];  // always [4,4]
				for (int i = 0; i < (4 * Nb); ++i)
				{
					this.State[i % 4, i / 4] = input[i];
				}

				AddRoundKey(0);

				for (int round = 1; round <= (Nr - 1); ++round)  // main round loop
				{
					SubBytes();
					ShiftRows();
					MixColumns();
					AddRoundKey(round);
				}  // main round loop

				SubBytes();
				ShiftRows();
				AddRoundKey(Nr);

				// output = state
				for (int i = 0; i < (4 * Nb); ++i)
				{
					output[i] = this.State[i % 4, i / 4];
				}
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "Cipher"); }

			return output;
		}  // Cipher()

		/// <summary>
		/// Decrypts a 16 byte block of text
		/// </summary>
		/// <param name="input">16 byte block to decrypt</param>
		/// <returns>16 byte block of decrypted bytes</returns>
		private byte[] InvCipher(byte[] input)  // decipher 16-bit input
		{
			byte[] output = new byte[16];

			try
			{
				// state = input
				this.State = new byte[4, Nb];  // always [4,4]
				for (int i = 0; i < (4 * Nb); ++i)
				{
					this.State[i % 4, i / 4] = input[i];
				}

				AddRoundKey(Nr);

				for (int round = Nr - 1; round >= 1; --round)  // main round loop
				{
					InvShiftRows();
					InvSubBytes();
					AddRoundKey(round);
					InvMixColumns();
				}  // end main round loop for InvCipher

				InvShiftRows();
				InvSubBytes();
				AddRoundKey(0);

				// output = state
				for (int i = 0; i < (4 * Nb); ++i)
				{
					output[i] = this.State[i % 4, i / 4];
				}
			}

			catch (Exception excep)
			{ AES_ShowError(excep, "InvCipher"); }

			return output;
		}  // InvCipher()

		#endregion // Private Encrypt and Decrypt

		#region AES Tables and Work Body

		private void SetNbNkNr(KeySize keySize)
		{
			this.Nb = 4;     // block size always = 4 words = 16 bytes = 128 bits for AES

			if (keySize == KeySize.Bits128)
			{
				this.Nk = 4;   // key size = 4 words = 16 bytes = 128 bits
				this.Nr = 10;  // rounds for algorithm = 10
			}
			else if (keySize == KeySize.Bits192)
			{
				this.Nk = 6;   // 6 words = 24 bytes = 192 bits
				this.Nr = 12;
			}
			else if (keySize == KeySize.Bits256)
			{
				this.Nk = 8;   // 8 words = 32 bytes = 256 bits
				this.Nr = 14;
			}
		}  // SetNbNkNr()

		private void BuildSbox()
		{
			this.Sbox = new byte[16, 16] {  // populate the Sbox matrix
												/* 0     1     2     3     4     5     6     7     8     9     a     b     c     d     e     f */
												/*0*/  {0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76},
												/*1*/  {0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0},
												/*2*/  {0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15},
												/*3*/  {0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75},
												/*4*/  {0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84},
												/*5*/  {0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf},
												/*6*/  {0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8},
												/*7*/  {0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2},
												/*8*/  {0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73},
												/*9*/  {0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb},
												/*a*/  {0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79},
												/*b*/  {0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08},
												/*c*/  {0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a},
												/*d*/  {0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e},
												/*e*/  {0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf},
												/*f*/  {0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16} };

		}  // BuildSbox() 

		private void BuildInvSbox()
		{
			this.iSbox = new byte[16, 16] {  // populate the iSbox matrix
												 /* 0     1     2     3     4     5     6     7     8     9     a     b     c     d     e     f */
												 /*0*/  {0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb},
												 /*1*/  {0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb},
												 /*2*/  {0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e},
												 /*3*/  {0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25},
												 /*4*/  {0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92},
												 /*5*/  {0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84},
												 /*6*/  {0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06},
												 /*7*/  {0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b},
												 /*8*/  {0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73},
												 /*9*/  {0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e},
												 /*a*/  {0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b},
												 /*b*/  {0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4},
												 /*c*/  {0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f},
												 /*d*/  {0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef},
												 /*e*/  {0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61},
												 /*f*/  {0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d} };

		}  // BuildInvSbox()

		private void BuildRcon()
		{
			this.Rcon = new byte[11, 4] { {0x00, 0x00, 0x00, 0x00},  
									   {0x01, 0x00, 0x00, 0x00},
									   {0x02, 0x00, 0x00, 0x00},
									   {0x04, 0x00, 0x00, 0x00},
									   {0x08, 0x00, 0x00, 0x00},
									   {0x10, 0x00, 0x00, 0x00},
									   {0x20, 0x00, 0x00, 0x00},
									   {0x40, 0x00, 0x00, 0x00},
									   {0x80, 0x00, 0x00, 0x00},
									   {0x1b, 0x00, 0x00, 0x00},
									   {0x36, 0x00, 0x00, 0x00} };
		}  // BuildRcon()

		private void AddRoundKey(int round)
		{

			for (int r = 0; r < 4; ++r)
			{
				for (int c = 0; c < 4; ++c)
				{
					this.State[r, c] = (byte)((int)this.State[r, c] ^ (int)w[(round * 4) + c, r]);
				}
			}
		}  // AddRoundKey()

		private void SubBytes()
		{
			for (int r = 0; r < 4; ++r)
			{
				for (int c = 0; c < 4; ++c)
				{
					this.State[r, c] = this.Sbox[(this.State[r, c] >> 4), (this.State[r, c] & 0x0f)];
				}
			}
		}  // SubBytes

		private void InvSubBytes()
		{
			for (int r = 0; r < 4; ++r)
			{
				for (int c = 0; c < 4; ++c)
				{
					this.State[r, c] = this.iSbox[(this.State[r, c] >> 4), (this.State[r, c] & 0x0f)];
				}
			}
		}  // InvSubBytes

		private void ShiftRows()
		{
			byte[,] temp = new byte[4, 4];
			for (int r = 0; r < 4; ++r)  // copy State into temp[]
			{
				for (int c = 0; c < 4; ++c)
				{
					temp[r, c] = this.State[r, c];
				}
			}

			for (int r = 1; r < 4; ++r)  // shift temp into State
			{
				for (int c = 0; c < 4; ++c)
				{
					this.State[r, c] = temp[r, (c + r) % Nb];
				}
			}
		}  // ShiftRows()

		private void InvShiftRows()
		{
			byte[,] temp = new byte[4, 4];
			for (int r = 0; r < 4; ++r)  // copy State into temp[]
			{
				for (int c = 0; c < 4; ++c)
				{
					temp[r, c] = this.State[r, c];
				}
			}
			for (int r = 1; r < 4; ++r)  // shift temp into State
			{
				for (int c = 0; c < 4; ++c)
				{
					this.State[r, (c + r) % Nb] = temp[r, c];
				}
			}
		}  // InvShiftRows()

		private void MixColumns()
		{
			byte[,] temp = new byte[4, 4];
			for (int r = 0; r < 4; ++r)  // copy State into temp[]
			{
				for (int c = 0; c < 4; ++c)
				{
					temp[r, c] = this.State[r, c];
				}
			}

			for (int c = 0; c < 4; ++c)
			{
				this.State[0, c] = (byte)((int)gfmultby02(temp[0, c]) ^ (int)gfmultby03(temp[1, c]) ^
					(int)gfmultby01(temp[2, c]) ^ (int)gfmultby01(temp[3, c]));
				this.State[1, c] = (byte)((int)gfmultby01(temp[0, c]) ^ (int)gfmultby02(temp[1, c]) ^
					(int)gfmultby03(temp[2, c]) ^ (int)gfmultby01(temp[3, c]));
				this.State[2, c] = (byte)((int)gfmultby01(temp[0, c]) ^ (int)gfmultby01(temp[1, c]) ^
					(int)gfmultby02(temp[2, c]) ^ (int)gfmultby03(temp[3, c]));
				this.State[3, c] = (byte)((int)gfmultby03(temp[0, c]) ^ (int)gfmultby01(temp[1, c]) ^
					(int)gfmultby01(temp[2, c]) ^ (int)gfmultby02(temp[3, c]));
			}
		}  // MixColumns

		private void InvMixColumns()
		{
			byte[,] temp = new byte[4, 4];
			for (int r = 0; r < 4; ++r)  // copy State into temp[]
			{
				for (int c = 0; c < 4; ++c)
				{
					temp[r, c] = this.State[r, c];
				}
			}

			for (int c = 0; c < 4; ++c)
			{
				this.State[0, c] = (byte)((int)gfmultby0e(temp[0, c]) ^ (int)gfmultby0b(temp[1, c]) ^
					(int)gfmultby0d(temp[2, c]) ^ (int)gfmultby09(temp[3, c]));
				this.State[1, c] = (byte)((int)gfmultby09(temp[0, c]) ^ (int)gfmultby0e(temp[1, c]) ^
					(int)gfmultby0b(temp[2, c]) ^ (int)gfmultby0d(temp[3, c]));
				this.State[2, c] = (byte)((int)gfmultby0d(temp[0, c]) ^ (int)gfmultby09(temp[1, c]) ^
					(int)gfmultby0e(temp[2, c]) ^ (int)gfmultby0b(temp[3, c]));
				this.State[3, c] = (byte)((int)gfmultby0b(temp[0, c]) ^ (int)gfmultby0d(temp[1, c]) ^
					(int)gfmultby09(temp[2, c]) ^ (int)gfmultby0e(temp[3, c]));
			}
		}  // InvMixColumns

		private static byte gfmultby01(byte b)
		{
			return b;
		}

		private static byte gfmultby02(byte b)
		{
			if (b < 0x80)
				return (byte)(int)(b << 1);
			else
				return (byte)((int)(b << 1) ^ (int)(0x1b));
		}

		private static byte gfmultby03(byte b)
		{
			return (byte)((int)gfmultby02(b) ^ (int)b);
		}

		private static byte gfmultby09(byte b)
		{
			return (byte)((int)gfmultby02(gfmultby02(gfmultby02(b))) ^
				(int)b);
		}

		private static byte gfmultby0b(byte b)
		{
			return (byte)((int)gfmultby02(gfmultby02(gfmultby02(b))) ^
				(int)gfmultby02(b) ^
				(int)b);
		}

		private static byte gfmultby0d(byte b)
		{
			return (byte)((int)gfmultby02(gfmultby02(gfmultby02(b))) ^
				(int)gfmultby02(gfmultby02(b)) ^
				(int)(b));
		}

		private static byte gfmultby0e(byte b)
		{
			return (byte)((int)gfmultby02(gfmultby02(gfmultby02(b))) ^
				(int)gfmultby02(gfmultby02(b)) ^
				(int)gfmultby02(b));
		}

		private void KeyExpansion()
		{
			this.w = new byte[Nb * (Nr + 1), 4];  // 4 columns of bytes corresponds to a word

			for (int row = 0; row < Nk; ++row)
			{
				this.w[row, 0] = this.key[4 * row];
				this.w[row, 1] = this.key[4 * row + 1];
				this.w[row, 2] = this.key[4 * row + 2];
				this.w[row, 3] = this.key[4 * row + 3];
			}

			byte[] temp = new byte[4];

			for (int row = Nk; row < Nb * (Nr + 1); ++row)
			{
				temp[0] = this.w[row - 1, 0]; temp[1] = this.w[row - 1, 1];
				temp[2] = this.w[row - 1, 2]; temp[3] = this.w[row - 1, 3];

				if (row % Nk == 0)
				{
					temp = SubWord(RotWord(temp));

					temp[0] = (byte)((int)temp[0] ^ (int)this.Rcon[row / Nk, 0]);
					temp[1] = (byte)((int)temp[1] ^ (int)this.Rcon[row / Nk, 1]);
					temp[2] = (byte)((int)temp[2] ^ (int)this.Rcon[row / Nk, 2]);
					temp[3] = (byte)((int)temp[3] ^ (int)this.Rcon[row / Nk, 3]);
				}
				else if (Nk > 6 && (row % Nk == 4))
				{
					temp = SubWord(temp);
				}

				// w[row] = w[row-Nk] xor temp
				this.w[row, 0] = (byte)((int)this.w[row - Nk, 0] ^ (int)temp[0]);
				this.w[row, 1] = (byte)((int)this.w[row - Nk, 1] ^ (int)temp[1]);
				this.w[row, 2] = (byte)((int)this.w[row - Nk, 2] ^ (int)temp[2]);
				this.w[row, 3] = (byte)((int)this.w[row - Nk, 3] ^ (int)temp[3]);

			}  // for loop
		}  // KeyExpansion()

		private byte[] SubWord(byte[] word)
		{
			byte[] result = new byte[4];
			result[0] = this.Sbox[word[0] >> 4, word[0] & 0x0f];
			result[1] = this.Sbox[word[1] >> 4, word[1] & 0x0f];
			result[2] = this.Sbox[word[2] >> 4, word[2] & 0x0f];
			result[3] = this.Sbox[word[3] >> 4, word[3] & 0x0f];
			return result;
		}

		private byte[] RotWord(byte[] word)
		{
			byte[] result = new byte[4];
			result[0] = word[1];
			result[1] = word[2];
			result[2] = word[3];
			result[3] = word[0];
			return result;
		}

		public void Dump()
		{
			Console.WriteLine("Nb = " + Nb + " Nk = " + Nk + " Nr = " + Nr);
			Console.WriteLine("\nThe key is \n" + DumpKey());
			Console.WriteLine("\nThe Sbox is \n" + DumpTwoByTwo(Sbox));
			Console.WriteLine("\nThe w array is \n" + DumpTwoByTwo(w));
			Console.WriteLine("\nThe State array is \n" + DumpTwoByTwo(State));
		}

		public string DumpKey()
		{
			string s = string.Empty;
			for (int i = 0; i < key.Length; ++i)
				s += key[i].ToString("x2") + " ";
			return s;
		}

		public string DumpTwoByTwo(byte[,] a)
		{
			string s = string.Empty;
			for (int r = 0; r < a.GetLength(0); ++r)
			{
				s += "[" + r + "]" + " ";
				for (int c = 0; c < a.GetLength(1); ++c)
				{
					s += a[r, c].ToString("x2") + " ";
				}
				s += "\n";
			}
			return s;
		}

		#endregion // AES Tables and Work Body

		#region Byte and String Conversions

		/// <summary>
		/// Converts a string to a byte array
		/// </summary>
		/// <param name="StrToConvert">the string to convert</param>
		private byte[] ConvertStringToByteArray(string StrToConvert)
		{
			return System.Text.ASCIIEncoding.ASCII.GetBytes(StrToConvert);
		}

		/// <summary>
		/// Converts a byte array to a string
		/// </summary>
		/// <param name="ByteToConvert"></param>
		/// <returns></returns>
		private string ConvertByteArrayToString(byte[] ByteToConvert)
		{
			StringBuilder sb = new StringBuilder();
			for (int i = 0; i < ByteToConvert.Length; i++)
			{
				// do not convert 0
				if (ByteToConvert[i] > 0)
					sb.Append(System.Convert.ToChar(ByteToConvert[i]));
			}

			return sb.ToString();
		}

		#endregion // Byte and String Conversions

		#region Misc Functions

		/// <summary>
		/// Display an error message
		/// </summary>
		/// <param name="excep">the exception</param>
		/// <param name="FunctionName">the name of the function that caused the error</param>
		private void AES_ShowError(Exception excep, string FunctionName)
		{
			StringBuilder errMsg = new StringBuilder();
			string nl = "\r\n";

			// build the error string
			errMsg.Append("An error has ocurred." + nl);
			errMsg.Append("Function: clsAES." + FunctionName.Trim() + nl);
			errMsg.Append("Source: " + excep.Source + nl);
			errMsg.Append("Error Description: " + nl + excep.Message);

			// throw the error
			throw new Exception(errMsg.ToString(), excep);
		}

		/// <summary>
		/// Returns the size of the array needed to meet BlockSize
		/// </summary>
		/// <param name="ArrayLen">the length of the current array</param>
		private int GetArraySize(int ArrayLen)
		{
			// if this is divisible by blocksize, return arraylen
			if ((BlockSize % ArrayLen) == 0)
				return ArrayLen;

			// return the new array size
			return (((ArrayLen / BlockSize) + 1) * BlockSize);
		}

		/// <summary>
		/// Converts an encrypted byte array and adds an extra number for each digit
		/// </summary>
		/// <param name="textB"></param>
		/// <returns></returns>
		public static string ConvertByteArrayToEncryptedByteString(byte[] textB)
		{
			StringBuilder sb = new StringBuilder();
			int j = 0;
			Random rnd = new Random();

			for (int i = 0; i < textB.Length; i++)
			{
				j = textB[i].ToString().Length;
				if (j == 3)
					sb.Append(string.Format("{0}{1}", textB[i].ToString().Trim(), rnd.Next(0, 9)));
				else if (j == 2)
					sb.Append(string.Format("0{0}{1}", textB[i].ToString().Trim(), rnd.Next(0, 9)));
				else if (j == 1)
					sb.Append(string.Format("00{0}{1}", textB[i].ToString().Trim(), rnd.Next(0, 9)));
			}
			return sb.ToString();
		}

		/// <summary>
		/// Converts an encrypted byte string (4 digit characters) to a byte array
		/// </summary>
		/// <param name="textStr"></param>
		/// <returns></returns>
		public static byte[] ConvertEncryptedByteStringToByteArray(string textStr)
		{
			byte[] textB = new byte[textStr.Length / 4];
			int j = 0, textStrLen = textStr.Length;
			for (int i = 0; i < textStrLen; i = i + 4)
				textB[j++] = System.Convert.ToByte(textStr.Substring(i, 3));

			return textB;
		}

		#endregion // Misc Functions
	}
}